Oh gosh, what a terrible situation hon. I'm SO sorry!! Double pain--- betraying boyfriend, betraying best friend. BOTH of them really let you down. I would not consider relationships with either of them other than the business of your boyfriend being a father to your shared child.
Very sorry. This is a lifetime messy situation. Very hurtful to you AND the kids. best of luck sweetie. Here if you need to talk
LittleBee95 is totally right!
I would be pissed off at her if I was you. How could your best friend sleep with your ex? If I was your best friend I would be angry with your boyfriend for leaving you while pregnant. I think she's a bit stupid to be honest. If she is pregnant. Is he going to leave her as well? Can you both have babies knowing that your kids will be siblings? It's just very wrong. I wouldn't call your best friend a friend for doing that. They are both in the wrong. If she willingly slept with him then you should be mad at both of them.